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Cell-mediated immunity (CMI) to mouse adenovirus (M-Ad) infection was studied by macrophage migration inhibition test (MMI) as one of in vitro correlates of CMI. Both direct and indirect tests showed clearly that migration of packed peritoneal exudate cells (PEC) (immune mouse or nonimmune guinea pig) was remarkably inhibited; MIF was produced by interactions between immune PEC and infected cell extracts and between immune spleen cells and infected cells or their extracts. The antigen(s) responsible for the above MMI was demonstrated in 6- to 12-hour infected ME cells, and FUdR-treated infected ME cells. Since under these conditions there is S antigen(s) synthesis but not capsid antigen synthesis, the antigen(s) concerned must be an S antigen(s). T cells sensitized to infected cells were shown to be required to induce MMI. The MMI is specific for M-Ad, since no cross MMI was observed between M-Ad and SV40 systems. Time course study of the development of CMI to M-Ad by MMI tests showed that CMI became detectable 4 days post-infection (pi), reached its peak level about 10 days pi, and faded away rapidly in about 10 days thereafter.

The topological relationship on the mouse adenovirus (M-Ad)-infected cell surface between virus-induced specific cell surface(s) antigens and serologically defined major histocompatibility antigens (H-2) was analyzed by the cap formation technique. Rhodamine-isothiocyanate (RITC)-labeled anti-S serum failed to stain the surface of virus-infected lymphoid cells which were pretreated with anti-H-2 serum and fluorescein isothiocyanate (FITC)-labeled anti-mouse immunoglobulin serum (anti-M-Ig) to cap the appropriate H-2 antigens. Conversely, the capping of the S antigens by pretreatment with anti-S followed by FITC anti-M-Ig serum induced cocapping of H-2 antigens. The β2 microglobulins (β2m) were also shown to be cocapped with S antigens by anti-β2m or by anti-S serum. The S antigens, however, did not cocap with mouse-immunoglobulins or Thyl. 2 antigens on virus-infected B or T lymphocytes, respectively. To further elucidate the molecular relationship between S and H-2 antigens, radio-iodinated virus-infected cells were solubilized with Nonidet P40 (NP40) and S antigens were precipitated with anti-S serum. When the precipitates were analysed with sodium dodecyl sulfate Polyacrylamide gel electrophoresis, two major peaks were seen at positions of molecules of about 45,000 and 12,000 daltons both of which corresponded with molecules which were observed when NP40 extracts of virus-infected or uninfected cells were precipitated with anti-H-2 serum. Sequential immunoprecipitation analysis of infected cell extracts showed that S antigens were coprecipitated with either H-2K or H-2D antigens. These results suggest that the S antigens are somehow associated with H-2K or H-2D antigens separately.

The type of effector cells in immune spleen cells (ISC) responsible for cell-mediated cytolysis of mouse adenovirus-infected cells was characterized. When ISC were pretreated with anti-mouse thymocyte or anti-Thy1.2 serum and complement, their cytolytic activity assayed by the 51 Cr release test was completely abolished, whereas it was not significantly reduced either when ISC were pretreated with anti-mouse immunoglobulin serum and complement or after ISC were kept standing at 37°C for 2 h in a plastic dish to remove adherent cells. These data indicate that the effector cells in ISC are T cells. The release of nonspecific or specific soluble cytotoxic factor(s) from ISC upon contact with mouse adenovirus-infected cells was not demonstrated, but about 30 U of interferon activity per ml was detected. However, 10 times as many units of exogenous interferon or more showed no effect on 51 Cr release from target infected cells or on the inhibition of viral antigen synthesis in infected cells. Experiments with mouse cells of different major histocompatibility antigens indicated that the cytotoxicity of ISC is effective when sensitizer and target cells share all or part of the same H-2 gene complex but not effective when they are of a different H-2 gene complex.

Migration of peritoneal exudate cells (PEC), which were prepared from mice immunized against mouse adenovirus (M-Ad), was inhibited upon exposure to the antigenic extract of M-Ad-infected cells. This inhibition was shown to be blocked when infected cells or their extracts were pretreated with antiserum against M-Ad-induced cell surface (S) antigen(s) or with antisera against alloantigens of infected cells. Immune spleen cell-mediated cytolysis of M-Ad-infected cells was also blocked in the presence of anti-S, anti-alloantigen or anti-beta 2m serum. Immunofluorescent antibody staining of S antigen(s) was blocked when infected cells were pretreated with anti-alloantigen or anti-beta 2m serum, whereas it was not blocked when they were pretreated with anti-mouse immunoglobulin or anti-Thy-1.2 serum. Conversely, immunofluorescent antibody staining of alloantigens was blocked when infected cells were pretreated with anti-S serum. These findings indicate that S and alloantigens are associated with each other or at least located very close to each other.

A virus-specific cell surface antigen(s) was detected on mouse adenovirus-infected cells by the immunofluorescent antibody technique. It was demonstrated in infected cells regardless of the mouse strain or animal species used. It became detectable on the cell surface about 6 h postinfection and was demonstrated in 90% of infected cells at 24 to 36 h postinfection. On the other hand, intracellular capsid antigens became detectable by the immunofluorescent antibody technique at about 24 h postinfection. Since it was also detected on virus-infected cells treated with 5′-fluorodeoxyuridine to block viral deoxyribonucleic acid synthesis, it was synthesized at the early stage of infection and may not be a virus structural component. The relationship between this serologically detectable cell surface antigen(s) and cell-mediated immune response to virus infections is discussed.